Water, in general, isn't specific enough. Hot water definitely won't help. It's low temperature, high thermal capacity / high latent heat of vaporization extinguishants that are best. The FAA has a whole protocol and training materials on how to put out Li-ion fires.
The latent heat of vaporization of water is so high that the temperature of liquid water can’t possibly make a big difference (specific heat is 4.18kJ/kg/K, latent heat of vaporization 2,260kJ/kg.)
